Many different types of portable electronic devices are in use today. In particular, notebook computers, palm-top computers, and personal digital assistants (PDA) are commonplace. The use of mobile telephones is also widespread and it is expected that in the near future combined mobile telephone/PDA devices will be widely used.
With portable electronic devices which store large amounts of data and/or operating instructions, there is often a need to transfer data between the portable device and a remote electronic device such as a computer or printer. Conventionally, such data transfer is achieved by providing both devices with serial input/output (I/O) ports (e.g. RS232) and by interconnecting these ports with an electrical cable. More recently, some portable electronic devices have been provided with an infra-red (IR) I/O port to allow devices to transfer data via a wireless infra-red transmission link. A wireless link avoids the need to connect a cable between the communicating devices, making the setting up of the transmission link a relatively simple procedure and also reducing costs. However, IR links do not function, or do not function well, where there is no direct line of sight between the communicating devices and/or where electromagnetic interference is present. Both of these problems can arise when it is desired to couple a mobile telephone/PDA device to some other electronic device, for example a hands-free controller, inside a vehicle. Often, the only solution to this problem is to provide portable electronic devices with an additional I/O port which can be connected via a cable to a remote device in the event that the IR link does not function satisfactorily.
Typically, the space occupied by, and complexity of an IR interface port is considerably less than that of an electromechanical I/O port. Hence IR links are extremely desirable where portable electronic devices are concerned. However, this advantage is lost when it is necessary to include both electromechanical and IR input ports in the same device. The need for two such ports also increases the cost of the device.